Of all the arguments and ideas posited in the intriguing “Sex at Dawn,” its dominant one is the most controversial: Humans are not, nor have ever been, wired for monogamy, and our societal insistence on it is indisputably harmful and punitive.

The concept isn’t new — Lewis Henry Morgan, a peer and friend of Charles Darwin, put forth the same argument in the 19th century, coining the term “omni-monogamous” to describe the baseline setting of human sexuality. The proof presented by authors Christopher Ryan and Cacilda Jetha, however, is new. “I was surprised — I started out with the passion of the convert when it came to evolutionary sexuality,” Ryan says. “But the data is overwhelming.”

“Sex at Dawn” begins by dismantling centuries-old conventional wisdom regarding human sexual behavior — that we mature, go through a period of sexual variety, then settle down with one person, forever. That concept came into being with agriculture, and the benefits were as much economic as societal. But the belief that such mores are ingrained in us, not the other way around, has somehow managed to persist even as human behavior continually proves the opposite — in America especially, where attitudes towards sex remain Puritan and binary. We are a culture that places the highest value on marriage and monogamy, yet porn generates more profit than pro football, baseball and basketball franchises combined.

“It’s an adolescent culture,” says Ryan, himself an American who’s lived in Spain for the past 20 years. “I think Americans adhere to their Hollywood mythology, the sense that love is sex, and sex is love, with its magic and spirituality.”

“Sex at Dawn” seeks to disabuse us of this notion.

In Russia, for example, sex on vacation doesn’t count. In France, adulterous affairs don’t necessarily lead to divorce; in America, infidelity is one of the top reasons marriages split up. In their book, Ryan and Jetha cite the 2007 work “Lust in Translation” and author Pamela Druckerman’s conclusion that more American women leave their marriages than want to, mainly because of societal pressure, the idea that it’s the only way for a betrayed spouse to reclaim dignity. “She refers to it as ‘the script,’” Ryan says. (Druckerman was shocked to hear from women who left their marriages over a one-night stand, “because ‘that’s what you do.’”)

America’s “spectacular failure of marriage,” Ryan says, is one of the most poignant arguments for a reassessment of our attitudes towards monogamy, to aggressively question whether we are, in fact, setting ourselves up for failure. Could it be that we may be more complicated than we know and, also, simpler? Our closest living relatives, after all, don’t have sex with just one mate. As the authors write, “Monogamy is not found in any social, group-living primate except — if the standard narrative is to be believed — us.”

This is not to say that romantic love and long-term pair-bonds are also societal constructs, or are less important than sex. Nor do the authors see love and bonding as better. Just different. (Primates, as it turns out, also exhibit behaviors once believed the sole province of humans: they hold and kiss each others’ hands, walk arm-in-arm, gaze into each other eyes. They do form bonds — but not every sexual encounter means that pair-bonds exist, or that they will result.)

The authors believe that if American attitudes towards sex could lighten up — and not in a juvenile, sex-farce way, but in a grown-up, every-encounter-isn’t-laden-with-import way — humanity would benefit. Like primates, our prehistoric ancestors used sex as currency, as a buffering mechanism, as a means to keep the group on an even keel; there’s a reason we have a sexual drive that doesn’t remain fixed on one mate. (Whether we choose to keep it there, they maintain, is possible — just not natural.)

“We see it like the war on drugs,” Ryan says of his and Jetha’s attempt to change the discourse. “There are a lot of parallels.” “It’s ‘just say no’ vs. harm reduction. We’re all at the point where we’re about to admit that marijuana use isn’t a big deal. Sexuality’s the same thing.”

As for the popular theory that romantic love is an evolutionary adaptation meant to prevent sexual infidelity, Ryan finds the notion flawed. Aside from scientific studies proving that women’s biology is perfectly designed to obscure paternity, and men’s designed to reproduce quickly and often, there is a philosophical distinction that Ryan says is the crux of the book’s argument.

“I would ask, what is meant by the word ‘love’?” he says. “Love that makes you want to share your life with someone and visit them in the hospital and take care of them when they’re dying — that’s different,” he says. “People in European cultures can see that love isn’t sex, and sex isn’t love. We should just accept the kind of animal we are.”